The Duke of Cambridge revealed the extent of his wife's morning sickness as he wryly joked that its name should be changed to reflect the fact she had been suffering night and day.

William was forced to go solo on Saturday evening as he attended the Winter Whites Gala in aid of homeless charity Centrepoint as Kate is resting after three days of treatment for a severe form of the illness earlier this week.

William, who is a patron of the charity, did not make any reference to the apparent suicide of nurse Jacintha Saldanha, 46, who fell for a hoax call that was made to the private hospital where the Duchess was being treated.

As he chatted to guests at London's Royal Albert Hall for his first public engagement since it was announced he is to become a father, the Duke was offered many congratulations on the happy news.

Former Centrepoint chairman Michael O'Higgens said William joked that the name of Kate's illness should be changed. Mr O'Higgens said: "He said they shouldn't call it morning sickness as it's a day and all night sickness."

He said he thought the Duke would make a great father, adding: "All I've seen of him is his amazing ability to relate to people and I think the care he's shown for his wife this week says a lot."

Looking smart in black tie, William sipped a soft drink and chatted with sponsors, donors and young people who have been helped by the charity at a drinks reception ahead of a meal.

The Duke said it was a "great pleasure" to be at the charity event as he later gave a speech. He told guests that some of the "most inspiring moments of my life" had been with the young people of Centrepoint.

Referring to the night he spent on the streets in 2009 to experience what it is like sleeping rough, he said: "Of course, this was just one night. I was cold but safe, and I knew I had a home waiting for me. Many others have no such luck. The cold streets are the only reality they know.

"And yet so often their spirit shines through. What these unfortunate men, women and young people could achieve given the right opportunities is limitless. I really believe that."